I need to make an adjustable power controller for a 3kW heater that will run off single-phase 240V AC power.
How should it be done?
Maybe a triac circuit similar to that used for dimming lights. Could this work? (Household heaters don't seem to ever be 'dimmable', is this just a cost saver, or is there another reason?)
An alternative idea was switch the heater on and off with a minimum interval of once per second in a PWM fashion, using a zero-cross solid state relay. But I don't think the neighbours would be happy with their lights flickering at 2Hz.
Any thoughts or other ideas would be appreciated
No need for phase angle modulation like on a dimmer for lighting, no need for PWM nor for switching on/off every second. It will introduce interference and the thermal capacity of the heater will be so large that you can easily switch on and off for full mains cycles and even every so many seconds (if your neighbors don't mind).
Switching at zero crossings is good practice, and a Solid State Relay can help you with that and is safe when properly connected.